The plight of polar bears in a changing climate is by now well-known, as the charismatic creatures rely on sea ice to hunt marine mammals. With fewer than 25,000 bears left in the wild, the rapid disappearance of sea ice is concerning. However, new research offers a touch of hope that polar bears may yet adapt to changing circumstances by replacing seal meals with animals found on land: caribou and snow geese.
The report comes from researchers Linda Gormezano and Robert Rockwell of the American Museum of Natural History in New York City. “Polar bears are opportunists and have been documented consuming various types and combinations of land-based food since the earliest natural history records," says Rockwell in a press release. By analyzing poler bear scat and watching the animals, the researchers knew that young bears, families and even some adult males were eating plants and animals during the ice-free period of the year.
Typically, polar bears stay on sea ice for as long as they can, dining on seals. During the summer months, they are forced to live on land where the assumption was that they didn’t eat much. Summer, a time of plenty for many species around the globe, is a months-long fast for polar bears. With declining ice levels predicted and observed, earlier studies forecast a potential grim end to the species.
Gormezano and Rockwell’s work shows that polar bears could theoretically survive on snow geese and caribou, fare many bears were already sampling. The researchers' predictions are based on polar bears living along the coast of the Western Hudson Bay. Polar bears there have been seen ambushing caribou using similar techniques they use to hunt seals. Eggs of snow geese are energetically easy to get and if the snow geese have enough food themselves, their population numbers don’t seem to suffer from polar bear predation.
Such sources of land food could be enough for adult male polar bears to survive, the researchers calculate. They published their findings in the journal PLOS One.
Eating geese and caribou isn’t the only new strategy researchers are noticing. Polar bears in Svaldbard, the Arctic islands north of Norway, have dined on dolphins trapped by ice as well. But some of the changes aren’t necessarily healthy for the bears. Food and waste from human towns prove attractive for hungry polar bears, but the close contact can provoke conflicts between our species and theirs. Rachel A. Becker reports for National Geographic that the town of Arviat in Nunavut Territory, Canada had to cancel trick-or-treating on Halloween last year for fear that polar bears would attack the revelers.
If the bears are going to adapt and survive, even in reduced numbers, the Arctic can expect a period of flux, at least until the effects of climate change are under control, Becker writes. "[I]t’s going to be a few more decades of these problems for animals that are dependent on ice,” Peter Ewins, leader of Arctic conservation for the World Wildlife Foundation told National Geographic. “We’re trying to help polar bears and local people survive through that transition.”